Principle Investigator: D.M. Allen. The Okanagan is one of the driest regions of Canada , and rapid development in the region due to both population and agricultural growth has significantly increased demands on both surface and groundwater resources. While exploitation of surface water is regulated, there is no current legislation governing the development and use of groundwater. This unregulated use of groundwater has the potential to have negative impacts on the sustainable development of the resource, and consequent negative impacts on long term social, economic, and agricultural activity in the watershed that rely on it. This Canadian Water Network project aims to enhance scientific understanding of groundwater recharge variability and mechanisms, and directly feed this understanding back to stakeholders through a series of targeted decision support tools.

An investigation of the impacts of climate change on groundwater recharge in the Oliver region of the southern Okanagan , BC (Mike Toews, M.Sc. Candidate)

Investigation of the linkages between low flows in streams, glacier melt and groundwater under climate change. (Collaborative research with Dr. Dan Moore, Department of Geography, University of British Columbia ). Project funded by the Climate Change Action Fund.

Nitrate Contamination: Abbotsford-Sumas Aquifer

Nitrate contamination of the trans-national Abbotsford-Sumas aquifer in the central Fraser Valley has become a significant problem over the last 30 years. Nitrate concentrations above the maximum allowable concentration (10 mg/L NO 3 -N) have been recorded in many of the aquifer's wells since the 1970's. Agricultural land-use above the aquifer is primarily raspberries, and although application practices for fertilizer have improved in recent years, nitrate concentrations in the aquifer have not dropped. Vadose zone transport simulations are being undertaken to determine the current loading to the aquifer . The loading concentrations are being applied to a 3D numerical groundwater model to investigate the transport of nitrate within the aquifer, both from historical and future perspectives.

Modelling the Impacts of Climate Change on Groundwater: A Comparative Study of Two Unconfined Aquifers in Southern British Columbia and Northern Washington State (Scibek, M.Sc. 2005). A methodology was developed for linking climate and groundwater models to investigate future impacts of climate change on groundwater resources using two case study sites of unconfined aquifers in southern British Columbia and northern Washington State . One semi-arid site is compared with one wet coastal site. The two groundwater systems differ in river-aquifer interactions, recharge, aquifer heterogeneity, scale, and groundwater use. Climate change scenarios from the Canadian Global Coupled Model 1 model runs for 1961-2000, 2010-2039, 2040-2069 and 2070-2099 are downscaled to local conditions, modelled at daily time scales using a stochastic weather generator, and applied to the spatially-distributed infiltration model. At one site the basin-scale runoff is also downscaled to predict river discharge and river-aquifer interactions in future climates. The impacts of predicted climate change on the groundwater system for each site are modelled in three-dimensions using Visual MODFLOW. Results and methodologies are compared and discussed. (Research Funded by Climate Change Action Fund, BC Ministry of Environment, and Environment Canada ).

Impacts of Predicted Climate Change on Groundwater Recharge, Gulf Islands , British Columbia , Canada (Appaih-Adjei, M.Sc. University of Lund , Sweden , 2006). This research investigated the potential impact of climate change on groundwater recharge to the fractured bedrock aquifers, which serve as the main source of potable water supply to the inhabitants of Gulf Islands in BC, Canada . Using Statistical DownScaling Model (SDSM) in combination with the LARS-WG stochastic weather generator, daily current and future (i.e., 2010-2039, 2040-2069, and 2070-2099) climate data were generated from CGCM1 predictions of the study location. These predictions were used as input to the HELP hydrologic model for estimation of recharge for the different climate change periods. The main properties of the aquifer – soil permeability, aquifer permeability and water table depth - used for recharge modeling were linked to ArcGIS for generating recharge zones, which allowed spatial and temporal integration of the recharge results. The combination of SDSM and LARS-WG in downscaling and predicting both the observed monthly temperature and precipitation was very successful. Mean annual precipitation downscaling with SDSM is predicted to increase by 52%, 65% and 88% relative to the observed for 2020's, 2050's and 2080's, respectively. On the other hand, the mean monthly temperature is predicted to rise by 1.14­­ o C in 2020's, 2.05 o C in the next 30 years, and up to 3.5 o C by the end of the century. According to HELP, the current mean annual recharge is about 44 % of the annual precipitation and is predicted to increase progressively by 7%, 8% and 9% in the 2020's, 2050's and 2080's, respectively, from the current.

Groundwater Resource Evaluation in Fractured Aquifers

Vulnerability Mapping Method for Fractured Rocks: DRASTICFm (in collaboration with S. Denny and M. Journeay, Geological Survey of Canada ). DRASTIC, the commonly-used methodology for mapping the intrinsic vulnerability of aquifers, is modified to incorporate the structural characteristics of fractured bedrock aquifers. In these aquifers, groundwater flow is predominantly through fractures, with large-scale fracture zones and faults acting as primary conduits for flow at the regional scale. The methodology is applied to the southern Gulf Islands region of southwestern British Columbia , Canada . Bedrock geology maps, soil maps, structural measurements, mapped lineaments, water well information, and topographic and bathymetric data, assembled within a comprehensive GIS database, form the basis for assigning traditional DRASTIC indices, while adding the structural indices necessary for capturing the importance of regional structural elements in recharge and well capture zone determinations.

A Hydrostructural Domain Approach to Quantifying Heterogeneity in Fractured Rock Aquifers, Gulf Islands, BC (M. Surrette, M.Sc., 2006). A hydrostructural domain approach was used to model regional scale groundwater flow in the fractured bedrock aquifers of the Gulf Islands , British Columbia , Canada . The domains were defined using fracture intensity and modeled using a stochastic, discrete fracture network-equivalent porous medium (DFN-EPM) approach. Results showed that the “highly” fractured interbedded sandstone and mudstone (<10 cm spacing) and fault and fracture domains had greater potential porosity than the “less” fractured sandstone (>1.0 m spacing) domain. The two highly fractured domains had an average permeability of 10 -13 m 2 compared to 10 -14 m 2 for the less fractured domain. The model results also showed a westward decrease in transmissivity, porosity and permeability. This decrease appears to be associated with the hinge line of a large anticline. Independently collected pump test analysis confirmed this interpretation. The DFN-EPM approach used in this thesis may have applications to other areas where groundwater resources in fractured rock aquifers are of interest.

The Role of Aquifer Heterogeneity in Saltwater Intrusion Modelling, Saturna Island , British Columbia ( E. Liteanu , M.Sc. 2003). Density-dependent flow and solute transport simulations were carried out using USGS SUTRA. Models simulations indicate that the magnitude of the permeability and the nature of layering exercise a major control of the magnitude and appearance of the freshwater-saltwater interface. The Pleistocene sea level history for the Gulf Islands , BC and chemical analyses for groundwater together suggest that saltwater intrusion on Saturna Island has two different origins: direct intrusion and older entrapped groundwater. A number of steady–state simulations were first undertaken to calibrate the model using groundwater geochemical data. To verify the model calibration, a transient simulation was conducted to simulate the behaviour of the freshwater-saltwater interface over the last 12,000 years. Over that time period, the island was submerged for a period of about 1,000 years, and rebounded, in a near instantaneous fashion with sea level at its current position. The transient simulations were undertaken to test if the period of 1,000 years of submergence was long enough to saturate the island with saltwater, and to test if the period following rebound is sufficient to result in the current observed saltwater-freshwater interface position. These simulations show that, considering the coarse approximations used in this research, the conceptual model is consistent with the Pleistocene sea level history for the area.

An Integrated Structural and Hydrogeological Investigation of the Fracture System in the Upper Cretaceous Nanaimo Group, Southern Gulf Islands , BC . (Mackie, M.Sc. 2002) The purpose of this collaborative study (with P. Mustard) was to identify differences in fracture distribution and character with respect to lithology and different generations of geologic structures, and to apply this fracture distribution and characterization to the development of a conceptual model for fractured controlled groundwater. A total of over 8000 fracture measurements were made at 157 stations on 8 islands using scanline, grid mapping and random data collection techniques. Results indicate that fracturing related to the Late Cretaceous to Neogene tectonic history is heterogeneously distributed and can be separated into groups. Four primary groups were identified: deformation bands, bedding-perpendicular fractures, faults and fracture zones, and non-bedding-perpendicular fractures. Relationships between structures, lithology and fracture spacing are used to define hydrostructural domains, areas of differing bulk permeability. Four domains are defined and supported by geochemical, geophysical and well yield data. The four domains are: discrete fault and fracture, fracture zone, bedding-perpendicular fracture, and fault zone. The bedding-perpendicular fracture domain includes two subdomains, the mudstone-dominant and sandstone-dominant domains. The fault zone and mudstone-dominant domain are the highest relative permeability. A methodology is proposed for delineating domains using a combination of lineament analysis and geologic mapping. The net effect has implications for flow system controls, the amount and location of recharge, and potential for saltwater intrusion along shorelines. Regional structural history is determined to have a direct and significant effect on groundwater resources via the distribution of brittle fractures.

Investigation of Potential Saltwater Intrusion Pathways in a Fractured Aquifer using an Integrated Geophysical, Geological and Geochemical Approach Borehole geophysics and horizontal loop electromagnetic profiling (Max-Min) were integrated with regional and site-scale geological and geochemical data to investigate the occurrence of, and possible pathways for, saltwater intrusion near fracture zones on a small island in British Columbia, Canada. An island-wide geochemical study identified a number of coastal wells that are contaminated by seawater; however, the occurrence of high salinity groundwater is spatially irregular due to variable fracturing of the bedrock. To investigate the influence of fracturing on the presence of high salinity groundwaters, geophysical investigations were undertaken at several sites. The nature of the bedrock permeability at these sites, with respect to lithology and fracture zone proximity, is described from geologic and hydrogeologic investigations and supported using surface EM profiling. Fractures and bedding contacts within boreholes, which were suspected to dominate bedrock permeability on the basis of outcrop studies, were identified using borehole video camera in conjunction with normal resistivity, spontaneous potential and natural gamma logs. Flow meter logs, acquired under a variety of aquifer stress conditions including static, tidal and pumping are used to identify potential water transmitting fractures and the locations of entry points for fresh and saline groundwater. The low flow rates measured under the various stress conditions confirm that groundwater flow is minimal and is restricted to mudstone units and single, generally sub-vertical fractures. The low natural groundwater discharge rates near the coast, even at close distances to fracture zones, may be key to the occurrence of saltwater intrusion on many parts of the island.

The Applicability and Scale Dependence of Aquifer Testing Methods: An Integrated Geophysical and Hydrogeological Characterization of Two Fractured Systems (Abbey, M.Sc. 2000). In this study, geological, horizontal loop electromagnetic (HLEM) and borehole geophysical surveys were used to characterize the lithology and structure of two fractured bedrock aquifers of low primary porosity (limestone/argillite and sandstone/mudstone), and to identify hydrostratigraphic and hydrostructural units and the associated boundary conditions. The applicability of constant-discharge aquifer testing and slug testing for determining hydraulic parameters of fractured aquifers was investigated by evaluating quantitatively each testing method and its associated analytical models (radial, linear, double porosity, unconfined). Pressure derivative analysis of the hydraulic test data aided in identifying boundary conditions and component flow regimes, thereby enhancing the analytical procedures.

Evaluation of the Analytical Methods Currently Used in B.C. to Analyze Hydraulic Test Data in Bedrock Aquifers This research project involved analyzing hydraulic test data from bedrock wells in British Columbia using various analytical techniques (both radial and linear flow models) to calculate the hydraulic parameters of the aquifers. The objectives of the study were to determine the range of values that are calculated using each method, to identify the most appropriate method of analysis, to estimate the possible error in using radial flow models when linear flow models are more suitable, and to recommend a strategy for analyzing test data from fractured rocks.

Nitrate Contamination and Modeling

A Study of Aquifer Heterogeneity and its Effects on Nitrate Transport and Distribution Using Geophysics and Numerical Groundwater Modelling in the Abbotsford-Sumas Aquifer, British Columbia, Canada and Washington State, USA (S. McArthur, M.Sc. 2006). Heterogeneity within the sand and gravel glacial outwash deposits of the Abbotsford-Sumas aquifer was investigated using ground penetrating radar (GPR) and borehole geophysical logging. Layering consists of fining upward sequences up to 5 m thick that are continuous over 10's of metres. Smaller heterogeneities were identified visually at a local gravel pit. Heterogeneity is best represented in a local scale groundwater model using vertical anisotropy based on the relative comparison of model travel times and groundwater ages. Model ages, however, are consistently underestimated. The spatial distribution of nitrate provides initial and calibration concentrations for the transport model. Observed concentrations are considerably higher than those predicted by the model, suggesting that either the source of nitrate used in the model is too low and that other sources should be considered (such as mobilization during summer when berries are irrigated), or that the current concentrations reflect a much longer history of contamination.

Stream Discharge and Hydrochemical Variation Over the Low Flow Season in the Abbotsford Aquifer , British Columbia (M.A. Berg, B.Sc. Honours, 2005). The Canadian portion of the Abbotsford-Sumas aquifer is located in the Lower Fraser Valley in southwest British Columbia . Understanding the interaction between the surface water and the groundwater in this aquifer is important in order to model the aquifer system response to potential climate change. Groundwater-surface water interactions are also important to understand for the protection of the endangered Nooksack Dace and Salish Sucker fish populations in the vicinity. This study was conducted on Fishtrap Creek, Pepin Brook, and Bertrand Creek . Regional flow measurements and chemistry sampling were conducted along the length of all three streams, and data were collected monthly. The water was sampled for physical parameters and dissolved chemical constituents. The study found groundwater discharging into Fishtrap Creek and Pepin Brook, and that both these streams have dissolved oxygen levels that fall below the accepted level for aquatic health. Nitrate levels also fluctuate in these streams and exceed background levels, indicating possible contamination. The low flow repeatability component of the study was conducted at two sites; one on Fishtrap Creek, and one on Bertrand Creek . The flow measurements were repeated across the channel, and down the length of a 7.5m section, and the results analyzed to determine the relation between the standard deviation, the percent error, and the mean discharge. At Bertrand Creek , there was a strong negative correlation (R 2 =0.9) between the percent error and the mean discharge. At Fishtrap Creek, the correlation was weak, and the results for that stream are inconclusive.

Aquifer Thermal Energy Storage

Influence Of Aquifer Heterogeneity On The Design And Modelling Of Aquifer Thermal Energy Storage (ATES) Systems (Bridger, M.Sc. 2006). A modelling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in aquifer thermal energy storage (ATES) systems. An existing ATES system installed within a heterogeneous aquifer system in Agassiz , British Columbia , Canada was used as a case study. Two 3D heat transport models of the study site were developed and calibrated using the heat transport code FEFLOW including: a “simple” model domain with uniform hydraulic and thermal properties (no layering); and, a “complex” aquifer domain with variable hydraulic and thermal properties assigned to discrete layers to represent aquifer heterogeneity. Comparison of simulation results indicated heat transport in higher permeability layers was significant. Effects of heterogeneity on thermal energy storage and recoverability were not observed. Heat transport in the aquifer was determined to be more sensitive to properties and boundary conditions which influence convective heat transport.

Stable Isotope and Geochemistry

Use of Stable Isotopes ( 206 Pb, 18 O and 2 H) in Delineating Plumes for Acid Rock Drainage Problems (Lepitre, M.Sc. 2001) This research project was a collaborative effort with Jim Mortinsen, University of British Columbia. The project involved sampling groundwaters and spring waters in the mine area of the Sullivan Mine in Kimberly, B.C. The mine is currently being decommissioned. The research demonstrated that stable isotopes of lead in combination with those of water can be used delineate or fingerprint mine effluent from tailings pond in acid rock drainage problem.

Integrated Geochemical and Stable Isotope Analysis of Tailings Effluent at the Seepage Collection System at the Sullivan Mine BC (Voormeij, B.Sc. 2001) This integrated study explored the combined use of hydrochemical data and stable isotopes, 18 O and 2 H, to characterize and quantify the origin and percentage of mixing between the tailings pond effluents, seepage collection and background waters at the Sullivan Mine, BC.

Chemical Evolution of Groundwater on the Gulf Islands (Suchy, B.Sc. 1998; Matsuo, B.Sc. 2001) These benchmark hydrochemical studies on Saturna Island and Hornby Island, B.C. were completed as undergraduate B.Sc. Honours theses and involved a large-scale sampling programs (funded by the Islands Trust) to investigate the chemical character of groundwaters and surface waters on the islands. The analyses were subsequently used to look at the evolution of groundwater in the Gulf Islands and to describe salinity variations on the islands.

Determining the Origin of Groundwater Using Stable Isotopes of 18 O, 2 H and 34 S (Allen) Stable isotopes of 18 O and 2 H in water and 34 S and 18 O in dissolved SO 4 are used to verify the interpretation of the chemical evolution and proposed sources of salinity for two islands located in southwest British Columbia. Results for d 18 O and d 34 S in SO 4 suggest a three component mixing between 1) atmospheric SO 4 derived largely from recharge of meteoric origin, 2) modern marine SO 4 associated with either modern day saltwater intrusion or Pleistocene-age seawater, and 3) terrestrial SO 4 . The age of the marine SO 4 is uncertain based on the geochemistry and SO 4 isotopes alone. Two options for mixing of saline groundwaters are proposed; either between current day marine SO 4 and atmospheric SO 4 , or between older (Pleistocene age) marine SO 4 and atmospheric SO 4 . d 18 O and d 2 H compositions are relatively consistent between both islands with a few samples showing evidence of mixing with water that is a hybrid mixture of Fraser River water and ocean water. The isotopic composition of this hydrid water is approximately d 18 O = 10 o / oo . d 18 O and d 2 H values for many saline groundwaters plot close to the global meteoric water line, which is distinctly different from the local meteoric water line. This suggests a meteoric origin for groundwaters that is different from the current isotopic composition of meteoric waters. It is proposed that these waters may be late Pleistocene in age and were recharged when the island was submerged below sea level and prior to rebound at the end of the last glaciation.